1. Field of the Invention
This invention relates to an improved fluid sample cell for the spectroscopic analysis of a fluid sample.
2. Description of the Prior Art
A number of fluid sample cells are known in the art for the containment of fluid samples during transmission spectroscopic analysis. The cells typically include one opening for the entrance and one opening for the exit of radiant energy, and are positioned in a spectroscopic instrument where a contained sample is irradiated with radiant energy. After passing through the sample, the radiant energy is detected and analyzed to determine the absorptive characteristics of the sample or a constituent thereof. The sample cell described herein represents an improvement over previously known sample cells of this type.
Many types of samples that undergo spectroscopic analysis must be maintained at narrowly defined, elevated temperatures during the analysis. If the temperature is not maintained within a narrow range, the analysis can be rendered inacurate by virtue of unwanted variations in the absorption characteristics of the sample. In the prior art, various means have been provided to effect the heating of spectroscopic samples, but the heating and maintenance of samples in appropriate temperature ranges has been deficient in the prior art devices in terms of accuracy, convenience and efficiency.
A fluid sample cell should also be provided with some means for samples to be introduced and removed. The introduction and removal of samples can be done batch-wise, wherein one sample is introduced and removed before another is introduced, or the introduction and removal can be effected in a continuous manner, whereby a first sample may be purged by the simultaneous introduction of a subsequent sample. Because spectroscopic instruments typically irradiate sample cells when the cell is in a horizontal position, and because samples are often introduced and/or removed from the cell while in this horizontal position, the sample cells of the prior art typically are provided with inlet and outlet ports that are disposed laterally of the sample compartment and which are intended to carry the sample when the cell is in the horizontal position. It has now been found that this lateral filling arrangement is deficient because it fails to efficiently introduce and purge samples.
When unwanted impurities are present in a sample that is analyzed, the analysis can be rendered inaccurate. Such impurities are defined broadly herein to include lighter gaseous impurities, such as air, in a liquid sample or heavier liquid impurities, such as water, in a gaseous sample. The term impurities is also intended to include portions of prior samples that are not completely purged when a subsequent sample is introduced. Many prior art systems fail to provide any convenient means for the removal of such impurities.
Thus, it can be seen that the sample cells of the prior art are deficient in a number of respects, and that there is a need in the art for an improved sample cell which corrects the aforementioned deficiencies. To this end, the present invention is directed. Other objectives of the present invention will become apparent from the following discussion.